Snow plows, until recently, have been classified as being either "one-way" plows or "reversible". A one-way plow has a non-symmetrical, funnel-shaped configuration that permits snow to be thrown outwardly and upwardly from one side of the plow. In the past, such plows have been committed by their fixed structure to a single side operation. Further, such plows are used only in an angled format which prevents them from being used to pile snow in the forward direction.
A "reversible" plow is symmetrical, usually rectangular in shape. Such plows can be set perpendicular to their line of travel to allow snow to be forwardly piled. Alternately, they may be angled to either side so as to scrape snow continuously off to one side. Lacking a conical or funnel-like shape, a reversible plow is not able to throw snow in the manner of a one-way plow.
As both formats of plow are often needed, it would be highly desirable to have a reversible plow that could readily function in the manner of a one-way plow. This, however, would require a snow plow with a moldboard which can be changed in shape.
For optimal operation, the surface of a one-way plow should be funnel-like in character. Towards the center of the road (furthest from the side or ditch where snow will be thrown) the plow need not be high. The snow received can be met by a relatively vertical and substantially curved moldboard surface which, combined with the retiring, angular orientation of such surface, will induce the snow to flow laterally towards the ejection end of the plow.
While this process of receiving and deflecting snow is occurring evenly across the entire front width of the plow, more and more snow is present in proceeding across the moldboard surface towards the ejection end. Further, for ideal operation, it is desirable for such snow to acquire both a sideways and an upwards velocity. This is in addition to the forward velocity that the snow acquires by reason of having been picked-up by the forward moving snow plow blade. The upwards velocity acquired by the snow, combined with its sideways velocity, will maximize the distance that the snow is thrown, once it is ejected from the plow. This is of great value as the further the snow is thrown, the less likely it is that it will have to be moved a second time on a further plowing. Also, well thrown snow is more likely to clear banks of snow that may accumulate on the sides of a roadway.
Balanced against all of the foregoing considerations is the need to minimize the amount of materials to be committed to forming the snow plow structure. A heavy plow is expensive to build and operate. An ideal combination reversible/one-way plow should be able to readily change from a symmetrical form to a funnel-like configuration without the presence of complex structural systems.
It has long been known to provide deflector plates along the upper edge of snow plow blades to prevent snow from over-flowing over the top of such blades. Examples include the following U.S. Pat. Nos.:
1,900,703 to Frink PA1 1,926,011 to Soule PA1 2,160,972 to Litchy PA1 2,160,973 to Litchy PA1 4,459,769 to Willis. PA1 (a) a supporting frame having: PA1 (b) a deformable moldboard, in the form of a resilient, flexible sheet having forward and rearward surfaces and upper and lower edges, such moldboard being mounted on such frame with the lower edge of the moldboard positioned along the lower moldboard support; PA1 (c) a guide bar positioned along the upper portion of the moldboard for supporting and aligning the upper edge of the moldboard; PA1 (d) joint means supported by the central support and connected to the guide bar to permit the guide bar to rotate in both the horizontal and vertical directions; and PA1 (e) extensible guide bar positioning means extending rearwardly from a lateral portion of the guide bar to the frame, preferably at a point on the central support post, PA1 (a) a longitudinal slot into which the top edge of the moldboard is interfitted; and PA1 (b) a pair of hinges connecting the moldboard to the guide bar at the respective outer ends of the guide bar,
Attempts have also been made to introduce a rough approximation of variable curvature into the surface of a scraper blade, vis U.S. Pat. No. 4,019,587 to Meisel in respect of an earth moving bulldozer blade.
U.S. Pat. No. 3,466,767 to Rubin describes a flexible-arc deflector for use on a snow thrower that may also be tilted to the left or right to improve the projection of snow.
In the snow plowing field, U.S. Pat. No. 4,254,564 to Rath has proposed elevating the alternate ends of an overhanging deflector portion on a reversible plow so as to improve its snow ejection efficiency and achieve, at least partially, the benefits of a one-way plow.
More recently U.S. Pat. Nos. 4,837,951 and 5,025,577 to Verseef have proposed deforming the upper portion of a flexible moldboard so as to obtain similar benefits to those sought by Rath. Both of these latter patents rely upon arcurate arms (mounted behind the moldboard) that are extended upwardly to tilt their upper ends forward in the direction of travel of the plow, carrying the outer corners of the moldboard along a similar path.
U.S. Pat. No. 5,079,866 to Farrell achieves a similar effect by a mechanism which couples a pair of spaced apart accurate, moldboard deforming arms to the mechanism for controlling the sideways, angled geometry of the plow. The result is to simultaneously deform the moldboard into one-way curvature when the blade is angled either to the right or left. Again, as with Verseef, Farrell relies upon use of rearwardly mounted, preformed arms that are curved in a fixed configuration to serve as ribs in supporting the outer ends of the moldboard and to position the respective outer ends of the moldboard to produce the desired contour.
Verseef operates by manipulating directly the upper, outer corners of the moldboard. Farrell endeavours to control the alignment of the upper edge of the moldboard by positioning a centrally suspended tubular moldboard "retention strip", that engages the top edge of the moldboard, with his two laterally placed accurate arms.
In both Farrell and Verseef, the accurate arms shift alternate sides of the top portion of the moldboard either forward and downward or upwards and backwards. In both cases, the controlling arms are separately supported on a frame which lies behind the moldboard and extends across the width of the plow. Such arms provide backing and support for the moldboard, simultaneously at both sides of the plow. There is no teaching in either patent about the preferred path that the upper edge of the moldboard should follow in being deformed from one configuration to another.
Against this background it would be desirable to provide a simpler structure and mechanism for controlling the contour of a deformable moldboard for reversible snow plows.
A further desirable objective in designing a snow plow with a deformable moldboard is that such moldboard should be mounted in such a way as to minimize stresses that arise from the when changing its contours from one shape to another.
It is with the foregoing objects and considerations in mind that the inventors herein have arrived at the present invention.
The invention in its general form will first be described, and then its implementation in terms of specific embodiments will be detailed with reference to the drawings following hereafter. These embodiments are intended to demonstrate the principle of the invention, and the manner of its implementation. The invention in its broadest and more specific forms will then be further described, and defined, in each of the individual claims which conclude this Specification.